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Say No to the Paywall of PCI-E Bifurcation

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Re: Say No to the Paywall of PCI-E Bifurcation

#11

Post by zamadatix »

bdhess wrote: post #3

More config options means more to test and support, so more cost. The manufacturers who are buying lower end motherboards/chipsets at scale don’t need the feature. And virtually no consumer installs a PCI-E device, ever. So basically, it’s an argument to make all computers more expensive, in order to subsidize hobbyists.

If motherboard vendors are doing this out of only leaving settings for the things they've properly QA'd and can guarantee to work 100% of the time then half of the settings of most boards are in need of disabling as well.

Re: Say No to the Paywall of PCI-E Bifurcation

#12

Post by zamadatix »

I miss the ~X99 era of HEDT where the price to go from the consumer Z77 class stuff in the article to the "workstation" class was very minimal. The low end "Xeon" processors were had all with the consumer Haswell models had, including single core performance and relative price equivalence, but you got 4 memory channels, the ability to drive massive amounts of memory, ECC support, and 40 PCIe lanes from the CPU.

Nowadays if you want to buy HEDT you either get a very fast version of the consumer part which is still extremely lane limited (limiting the usefulness of features like bifurcation), still has 2 memory channels, has the same memory capacity limits as that 10 year old X99 platform, and may or may not have usable ECC support (depending on the particular board and/or platform chipset options for that year) OR you can spend way more to get a CPU which is worse performing unless you need 32+ cores (and the even higher cost associated with that) but at least the platform has all that original HEDT capability.

The 1st generation of Threadripper was a bit like that too, albeit AMDs CPUs weren't the top performers of the day when that came out and they've since gone up accordingly.

Re: Say No to the Paywall of PCI-E Bifurcation

#14

Post by hkgjjgjfjfjfjf »

winocm wrote: post #5
hakfoo wrote: post #4

Earlier quoted context omitted.

I'm sort of amazed these days that we still have commercial BIOSes (well, UEFIs) They're not a selling point, even for the enthusiasts who buy individual motherboards. You'd think that that by now, the chipset vendors would provide a reference Coreboot image for each new platform, (which, since it would be more or less for debugging purposes, would have MAX OPTIONS) and then the motherboard manufacturers would do the…

Honestly, if someone made a reference platform setup utility (and BDS initialization screen) for EFI systems with a familiar-ish UI and got it into upstream git, then I think a lot of the value add of commercial firmware would probably dissipate.

Tianocore

Re: Say No to the Paywall of PCI-E Bifurcation

#15

Post by freeone3000 »

nisegami wrote: post #13
nubinetwork wrote: post #10

Most CPUs don't have the lanes for this anyways... after you install a video card and an NVME drive, you're lucky if you have 8 lanes to spare, let alone 16...

Isn't that exactly why bifurcation is desirable?

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

Re: Say No to the Paywall of PCI-E Bifurcation

#16

Post by reginald78 »

bdhess wrote: post #3

More config options means more to test and support, so more cost. The manufacturers who are buying lower end motherboards/chipsets at scale don’t need the feature. And virtually no consumer installs a PCI-E device, ever. So basically, it’s an argument to make all computers more expensive, in order to subsidize hobbyists.

If the board has PCI-E slots, it should support their features. If customers never used them they would have been dropped for cost reasons and no one would care. And indeed there are plenty of mini PCs and laptops where that is the case. Presumably people not buying those have their reasons.

Re: Say No to the Paywall of PCI-E Bifurcation

#17

Post by myself248 »

freeone3000 wrote: post #15
nisegami wrote: post #13

Earlier quoted context omitted.

Isn't that exactly why bifurcation is desirable?

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

Right, but if there's 8 lanes to spare, and I could use 4 for a 10GbE NIC and 4 for another NVMe drive, that's better than wasting all 8 on one of those functions and not being able to install the other at all.

Re: Say No to the Paywall of PCI-E Bifurcation

#18

Post by atmanactive »

freeone3000 wrote: post #15
nisegami wrote: post #13

Earlier quoted context omitted.

Isn't that exactly why bifurcation is desirable?

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

The problem is the physical slot waste. If you have x16 slot and you put an x16 GPU card into it (like majority of people do), then, there is no waste whatsoever. But, if you put an x8 GPU or some other x4 or x1 card, then, there is a lot of PCIe lanes wasted, simply because you can't physically access them anymore. When your MBD can bifurcate, for example x8+x8, then, a £10 PCIe dongle can split that one x16 PCIe slot into two x8 PCIe slots.

Re: Say No to the Paywall of PCI-E Bifurcation

#19

Post by 3np »

atmanactive wrote: post #18
freeone3000 wrote: post #15

Earlier quoted context omitted.

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

The problem is the physical slot waste. If you have x16 slot and you put an x16 GPU card into it (like majority of people do), then, there is no waste whatsoever. But, if you put an x8 GPU or some other x4 or x1 card, then, there is a lot of PCIe lanes wasted, simply because you can't physically access them anymore. When your MBD can bifurcate, for example x8+x8, then, a £10 PCIe dongle can split that one x16 PCIe sl…

And if you ever have 1-4 spare slots, you could always fit another SSD or USB ports in there. Also keeping in mind that PCIe being package-switched, you can actually have a good time connecting more lanes than the CPU s set up for as long as you're not going full throttle on all cylinders and the chipset can cope :)

Re: Say No to the Paywall of PCI-E Bifurcation

#20

Post by 3np »

freeone3000 wrote: post #15
nisegami wrote: post #13

Earlier quoted context omitted.

Isn't that exactly why bifurcation is desirable?

Bifurcation lets you allocate the lanes in more configurations, but doesn’t actually give you more lanes or allow you to dynamically allocate a lane. Unless you’re connecting more devices than are planned for by the cpu and chipset, you’re not going to see an advantage.

It's fine to underprovision lanes. PCIe is packet-switched.
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